Detalles de publicación
PP 015096
Swift J1357.2-0933: a massive black hole in the Galactic thick disc
(1) IAC, (2) Departamento de astrofísica de la Univ. de La Laguna, (3) Instituto de Astrofísica de la Pontificia Universidad Católica de Chile
Swift J1357.2-0933 is one of the shortest orbital period black hole X-ray transients (BHTs). It exhibited deep optical dips together with an extremely broad H-alpha line during outburst. We present 10.4-m GTC time-resolved spectroscopy during quiescence searching for donor star absorption features. The large contribution of the accretion flow to the total luminosity prevents the direct detection of the companion. Nevertheless, we constrain the non-stellar contribution to be larger than ∼80% of the total optical light, which sets new lower limits to the distance (d > 2.29 kpc) and the height over the Galactic plane (z > 1.75 kpc). This places the system in the Galactic thick disc. We measure a modulation in the centroid of the H-alpha line with a period of P=0.11±0.04 d which, combined with the recently presented FWHM-K_2 correlation, results in a massive black hole (M_1 >9.3 M⊙) and a ∼M2V companion star (M_2 ∼ 0.4 M⊙). We also present further evidence supporting a very high orbital inclination (i ≥ 80º).